Sometimes (or rather frequently!) you read an article and you think.. uhm, well I already knew that. In that case, it still comes in handy to have something written by others that support your views (let alone the fact that it's nice to see your views confirmed too :)). Nancy Baym wrote an article called the new shape of online community: the example of Swedish independent music fandom. I know Abba, but didn't know Sweden is so important as a music hub...She uses a participant-observation analysis of Swedish music fan's interactions on the internet to show that sites are interlinked at multiple levels. Online communities have taken new forms between the site-based online group and the egocentric network.
She illustrates her point with the examples of the REM fan base, which started with a mailing list in the late 80s. Today, there are many other fan-created websites that co-exist. Plus there has been a rise in fan-authored MP3 blogs too. "Many of the bloggers link to one another through blog rolls, creating a multi-sited community of like-minded bloggers who interact through their posts and comments." With new incarnation of online fandom, the previous forms have not disappeared.
Mapping the boundaries becomes a challenge though. The Swedish indie fan community, for instance, is distributed throughout many places on the internet and off. Over time, active fans will bump into each other, and a sense of community may be formed, which has a lot of similarity with physical places. Few people visit every place in town, but in regular places, the same people may bump into eachother (school, sport clubs, restaurants, etc).
Apparently, it has been the norm for scientists to study an online space (as one URL) and study it. But that's a limited approach, given the interconnectedness of the various sites.
For developers it has consequences too; the challenge is to make sure site can serve as location of activity, and im- and export from other sites.
Ning is a good, positive example, I was able to feed my blog into my personal page on the forum, and to set up an delicious feed within 2 minutes.